Drive train and operating method for a hybrid vehicle with an overrun-enabled forward gear

Abstract

The invention relates to a drive train for a hybrid vehicle with an internal combustion engine, with a transmission and with an electric machine, wherein the electric machine is arranged between the internal combustion engine and the transmission. The drive train can be provided in a simple, economical and/or space-saving manner in that the transmission comprises at least one overrun-enabled forward gear transmitting traction torque only and at least one overrun-free forward gear. A hybrid vehicle can be operated with a drive train of this kind easily and efficiently in that, when an overrun-enabled forward gear transmitting only traction torque is engaged and while the vehicle speed lies below a certain engagement speed for an overrun-free forward gear and at least one criterion for the presence of a driving torque is established or satisfied, the transmission is shifted into the overrun-free forward gear.

What is claimed is: 
     
       1. A drive train for a hybrid vehicle with an internal combustion engine, with a transmission and with an electric machine, wherein the electric machine is arranged between the internal combustion engine and the transmission, wherein the transmission has at least one overrun-enabled forward gear transmitting only traction torque between the electric machine and at least one wheel of the hybrid vehicle and at least one overrun-free forward gear. 
     
     
       2. The drive train of  claim 1 , wherein the transmission has at least one overrun-enabled, low forward gear transmitting only traction torque and at least one overrun-free, higher forward gear. 
     
     
       3. The drive train of  claim 1 , wherein the drive train has a K 0  clutch arranged between the internal combustion engine and the electric machine; wherein the K 0  clutch is operable to recuperate energy by means of the electric machine and/or is closed to brake the vehicle by means of a drag torque by the internal combustion engine. 
     
     
       4. The drive train of  claim 1 , wherein the transmission is designed as one or more of a multi-stage transmission and a dual-clutch transmission. 
     
     
       5. An operating method for a hybrid vehicle with a drive train of  claim 1 , wherein, when an overrun-enabled forward gear of the transmission transmitting only traction torque is engaged and while the vehicle speed is below a certain engagement speed for an overrun-free forward gear of the transmission and at least one criterion for the presence of a driving torque is established or satisfied, the transmission is shifted into the overrun-free forward gear. 
     
     
       6. The operating method of  claim 5 , wherein, by shifting into the overrun-free forward gear, a drag torque is generated by one or more of the electric machine, to recuperate energy and to brake the vehicle, and by the internal combustion engine to brake the vehicle. 
     
     
       7. The operating method of  claim 5 , wherein one of more of
 the presence of a neutral accelerator pedal position, and 
 the presence of a non-zero vehicle speed, and 
 the presence of an inclination of a vehicle, and 
 the presence of a difference in rotational speed ahead of and behind the freewheel 
 is used as a criterion for the presence of a driving torque. 
 
     
     
       8. The operating method of  claim 5 , wherein the overrun-enabled forward gear transmitting only traction torque is maintained over a defined duration and the transmission is only shifted into the overrun-free forward gear when the at least one criterion for the presence of a driving torque is present or satisfied at the end of the defined duration and/or exceeds a certain threshold value for this. 
     
     
       9. The operating method of  claim 5 , wherein the charge level of a battery of the vehicle is established,
 wherein in the case of an incomplete charge of the battery, the transmission is shifted into the overrun-free forward gear to brake the vehicle using a drag torque through recuperation by the electric machine, and/or 
 wherein in the case of a full charge of the battery, the vehicle is braked by a brake. 
 
     
     
       10. An operating method for a hybrid vehicle with a drive train with an internal combustion engine, a transmission, and an electric machine; wherein the electric machine is arranged between the internal combustion engine and the transmission; wherein, when an overrun-enabled forward gear of the transmission transmitting only traction torque is engaged and while a vehicle speed is below a certain engagement speed for an overrun-free forward gear of the transmission and at least one criterion for the presence of a driving torque is established or satisfied, the transmission is shifted into the overrun-free forward gear;
 wherein the drive train has a K 0  clutch between the internal combustion engine and the electric machine, wherein the K 0  clutch is opened to recuperate energy by means of the electric machine and/or is closed to brake the vehicle by means of a drag torque by the internal combustion engine. 
 
     
     
       11. An operating method for a hybrid vehicle with a drive train with an internal combustion engine, a transmission, and an electric machine; wherein the electric machine is arranged between the internal combustion engine and the transmission; wherein, when an overrun-enabled forward gear of the transmission transmitting only traction torque is engaged and while a vehicle speed is below a certain engagement speed for an overrun-free forward gear of the transmission and at least one criterion for the presence of a driving torque is established or satisfied, the transmission is shifted into the overrun-free forward gear;
 wherein the presence of an inclination of the vehicle is detected when, over a certain period of time, the inclination is on average greater than a certain inclination threshold value. 
 
     
     
       12. The operating method of  claim 5 , wherein, when no criterium for the presence of a driving torque is established or satisfied, the overrun-enabled forward gear transmitting only traction torque is maintained and, insofar as the vehicle speed is below the certain engagement speed) for the overrun-free forward gear, it is established once again whether at least one criterion for the presence of a driving torque is present or satisfied. 
     
     
       13. The operating method of  claim 5 , wherein the overrun-enabled forward gear transmitting only traction torque is a low forward gear of the transmission and the overrun-free forward gear is a higher forward gear of the transmission. 
     
     
       14. The operating method of  claim 5 , wherein the transmission is designed as one or more of a multi-stage transmission and as a dual-clutch transmission. 
     
     
       15. The drive train of  claim 2 , wherein the drive train has a K 0  clutch arranged between the internal combustion engine and the electric machine; wherein the K 0  clutch is operable to recuperate energy by means of the electric machine and/or is closed to brake the vehicle by means of a drag torque by the internal combustion engine. 
     
     
       16. The drive train of  claim 2 , wherein the transmission is designed as one or more of a multi-stage transmission and a dual-clutch transmission. 
     
     
       17. The drive train of  claim 3 , wherein the transmission is designed as one or more of a multi-stage transmission and a dual-clutch transmission. 
     
     
       18. The operating method of  claim 6 , wherein one of more of
 the presence of a neutral accelerator pedal position, and 
 the presence of a non-zero vehicle speed, and 
 the presence of an inclination of a vehicle, and 
 the presence of a difference in rotational speed ahead of and behind the freewheel 
 is used as a criterion for the presence of a driving torque. 
 
     
     
       19. The operating method of  claim 6 , wherein the overrun-enabled forward gear transmitting only traction torque is maintained over a defined duration and the transmission is only shifted into the overrun-free forward gear when the at least one criterion for the presence of a driving torque is present or satisfied at the end of the defined duration and/or exceeds a certain threshold value for this. 
     
     
       20. The operating method of  claim 7 , wherein the overrun-enabled forward gear transmitting only traction torque is maintained over a defined duration and the transmission is only shifted into the overrun-free forward gear when the at least one criterion for the presence of a driving torque is present or satisfied at the end of the defined duration and/or exceeds a certain threshold value for this.